The plant lectin concanavalin A (Con A) from jack bean and the two lima bean lectins, a tetramer LBL4 and an octamer LBL8, are being studied. The relationship of the metal ion requirements and saccharide-binding activity are being examined by a variety of physical techniques. Transition metal ions such as Mn2+ and Ca2+ are necessary for inducing saccharide-binding activity in Con A. A succinylated derivative of Con A is being studied for metal-binding characteristics. This derivative is a well-behaved analog with properties similar to those of the native lectin. Metal ion-binding properties are being studied by magnetic resonance and fluorescence techniques. LBL4 and LBL8 binding to erythrocytes and lymphocytes have shown that those lectins bind with positive cooperativity to type A and AB erythrocytes but show no cooperativity with lymphocytes. As LBL8 is a potent mitogen, cooperativity is not important to the mitogenic response. One goal of this research is to develop these lectins for useful membrane probes. Metal ions activate the lima bean lectins and many others. Conformational changes occurring following metalation in LBLy and peanut agglutinin appear to be similar. The three lectins are being compared; our previous work with Con A is the basis for much of the future experimental design. Interleukin-2 (IL-2) from both horses and cattle have been characterized. Using our chosen lectins, we are establishing long-term cell lines and examining IL-2 receptor expression in stimulated lymphocytes and viral suppression and development of cytotoxic lymphocytes. (A)